[PATCH 2/3] powerpc/mm/hash: Avoid multiple HPT resize-ups on memory hotplug
From: Leonardo Bras <hidden>
Date: 2021-03-12 07:32:57
Also in:
lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
Every time a memory hotplug happens, and the memory limit crosses a 2^n value, it may be necessary to perform HPT resizing-up, which can take some time (over 100ms in my tests). It usually is not an issue, but it can take some time if a lot of memory is added to a guest with little starting memory: Adding 256G to a 2GB guest, for example will require 8 HPT resizes. Perform an HPT resize before memory hotplug, updating HPT to its final size (considering a successful hotplug), taking the number of HPT resizes to at most one per memory hotplug action. Signed-off-by: Leonardo Bras <redacted> --- arch/powerpc/include/asm/book3s/64/hash.h | 2 ++ arch/powerpc/include/asm/sparsemem.h | 2 ++ arch/powerpc/mm/book3s64/hash_utils.c | 14 ++++++++++++++ arch/powerpc/mm/book3s64/pgtable.c | 6 ++++++ arch/powerpc/platforms/pseries/hotplug-memory.c | 6 ++++++ 5 files changed, 30 insertions(+)
diff --git a/arch/powerpc/include/asm/book3s/64/hash.h b/arch/powerpc/include/asm/book3s/64/hash.h
index d959b0195ad9..843b0a178590 100644
--- a/arch/powerpc/include/asm/book3s/64/hash.h
+++ b/arch/powerpc/include/asm/book3s/64/hash.h@@ -255,6 +255,8 @@ int hash__create_section_mapping(unsigned long start, unsigned long end, int nid, pgprot_t prot); int hash__remove_section_mapping(unsigned long start, unsigned long end); +void hash_memory_batch_expand_prepare(unsigned long newsize); + #endif /* !__ASSEMBLY__ */ #endif /* __KERNEL__ */ #endif /* _ASM_POWERPC_BOOK3S_64_HASH_H */
diff --git a/arch/powerpc/include/asm/sparsemem.h b/arch/powerpc/include/asm/sparsemem.h
index d072866842e4..16b5f5300c84 100644
--- a/arch/powerpc/include/asm/sparsemem.h
+++ b/arch/powerpc/include/asm/sparsemem.h@@ -17,6 +17,8 @@ extern int remove_section_mapping(unsigned long start, unsigned long end); extern int memory_add_physaddr_to_nid(u64 start); #define memory_add_physaddr_to_nid memory_add_physaddr_to_nid +void memory_batch_expand_prepare(unsigned long newsize); + #ifdef CONFIG_NUMA extern int hot_add_scn_to_nid(unsigned long scn_addr); #else
diff --git a/arch/powerpc/mm/book3s64/hash_utils.c b/arch/powerpc/mm/book3s64/hash_utils.c
index cfb3ec164f56..1f6aa0bf27e7 100644
--- a/arch/powerpc/mm/book3s64/hash_utils.c
+++ b/arch/powerpc/mm/book3s64/hash_utils.c@@ -858,6 +858,20 @@ int hash__remove_section_mapping(unsigned long start, unsigned long end) return rc; } + +void hash_memory_batch_expand_prepare(unsigned long newsize) +{ + /* + * Resizing-up HPT should never fail, but there are some cases system starts with higher + * SHIFT than required, and we go through the funny case of resizing HPT down while + * adding memory + */ + + while (resize_hpt_for_hotplug(newsize, false) == -ENOSPC) { + newsize *= 2; + pr_warn("Hash collision while resizing HPT\n"); + } +} #endif /* CONFIG_MEMORY_HOTPLUG */ static void __init hash_init_partition_table(phys_addr_t hash_table,
diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
index 5b3a3bae21aa..f1cd8af0f67f 100644
--- a/arch/powerpc/mm/book3s64/pgtable.c
+++ b/arch/powerpc/mm/book3s64/pgtable.c@@ -193,6 +193,12 @@ int __meminit remove_section_mapping(unsigned long start, unsigned long end) return hash__remove_section_mapping(start, end); } + +void memory_batch_expand_prepare(unsigned long newsize) +{ + if (!radix_enabled()) + hash_memory_batch_expand_prepare(newsize); +} #endif /* CONFIG_MEMORY_HOTPLUG */ void __init mmu_partition_table_init(void)
diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
index 8377f1f7c78e..353c71249214 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c@@ -671,6 +671,8 @@ static int dlpar_memory_add_by_count(u32 lmbs_to_add) if (lmbs_available < lmbs_to_add) return -EINVAL; + memory_batch_expand_prepare(memblock_phys_mem_size() + lmbs_to_add * drmem_lmb_size()); + for_each_drmem_lmb(lmb) { if (lmb->flags & DRCONF_MEM_ASSIGNED) continue;
@@ -734,6 +736,8 @@ static int dlpar_memory_add_by_index(u32 drc_index) pr_info("Attempting to hot-add LMB, drc index %x\n", drc_index); + memory_batch_expand_prepare(memblock_phys_mem_size() + + drmem_info->n_lmbs * drmem_lmb_size()); lmb_found = 0; for_each_drmem_lmb(lmb) { if (lmb->drc_index == drc_index) {
@@ -788,6 +792,8 @@ static int dlpar_memory_add_by_ic(u32 lmbs_to_add, u32 drc_index) if (lmbs_available < lmbs_to_add) return -EINVAL; + memory_batch_expand_prepare(memblock_phys_mem_size() + lmbs_to_add * drmem_lmb_size()); + for_each_drmem_lmb_in_range(lmb, start_lmb, end_lmb) { if (lmb->flags & DRCONF_MEM_ASSIGNED) continue;
--
2.29.2